Locally Enhanced Dissolution Rate as a Probe for Nanocontact-Induced Densification in Oxide Glasses

Abstract

Atomic force microscopy (AFM) was used to characterize the surface damage (nanoindentations) effect on the chemical durability of glass surfaces (silica and soda-lime silicate glasses, WG). In basic solutions, an enhanced dissolution rate is reported and quantified at indentation sites (+10.5 nm/h and +52 nm/h for silica and WG, respectively) whereas none was observed once the indented surfaces were thermally annealed at 0.9 × T(g) for 2 h, a thermal treatment known for curing high pressure-induced permanent densification in oxides glasses. A direct link between high pressure-induced structural modifications encountered during nanoindentation and the measured dissolution rates is established. It is shown that this property conjointly used with the high resolution of the atomic force microscope may be used for probing, at the nanometer scale, the size and the nature of the structurally modified area underneath residual nanoindentation impressions. As an example, for 10 mN Vickers nanoindentations on WG, the zone affected by the permanently and structurally modified zone under the residual impression is found to be equal to (741 ± 30) nm with a transition zone thickness from the fully densified material to the elastically deformed one ranging between 115 and 165 nm.

Perfectly plastic flow in silica glass

“…Due to the slightly asymmetric geometry and the boundary conditions at the top and bottom of the pillar, strong strain gradients are predicted. In view of the small size of the sample, experimental mapping of these gradients is a presently insuperable challenge for local characterization methods [23,32,20]. The calculated densification distributions are plotted in 11.…”

“…Many investigations dealing with silica micro-plasticity have been carried out with high hydrostatic pressure experiments [30,13]; they are very useful, but lack the necessary shear contribution. It has also been proposed to use the indentation-induced densification field, which can be measured by Raman scattering [23,31], or by silica dissolution experiments [32], but there are discrepancies between these data.…”

Breaking the Limit of Micro‐Ductility in Oxide Glasses

“…Astonishingly, the entire cavity has recovered above the glass surface, with substantial amount of protrusion surrounding the point of indenter contact. [42] By placing a small indent close to the edge of a pre-existing larger indent, Gross and Tomozawa showed that hardness depends on the fictive temperature of the glass, and that the magnitude of the change in hardness depends on the chemical composition of the glass. This behavior suggests that swelling, presumably linked to atomic-scale reorganization of the structure, is occurring.…”

Competing Indentation Deformation Mechanisms in Glass Using Different Strengthening Methods

“…Emerging demand for stronger and lighter car windshields and other novel transparent structural materials further stimulates a need for deeper understanding and improvement of glass strengthening techniques. Studies of contact cracking (Lawn and Wilshaw, 1975;Ostojic and McPherson, 1987;Cook and Pharr, 1990) date back at least one century (Johnson, 1985;Lawn, 1998) and tremendous progress has been achieved to understand the shear flow, densification, and cracking under indentation in brittle solids (Lawn and Swain, 1975;Lawn and Wilshaw, 1975;Marshall and Lawn, 1978;Hagan, 1979;Lawn et al, 1983;Johnson, 1985;Ostojic and McPherson, 1987;Cook and Pharr, 1990;Lawn, 1998Lawn, , 2004Perriot et al, 2006;Gross and Tomozawa, 2008a,b,c;Gross et al, 2009;Kato et al, 2010;Gross, 2012a;Kassir-Bodon et al, 2012;Niu et al, 2012;Tran et al, 2012;Kjeldsen et al, 2013;Smedskjaer et al, 2013;Striepe et al, 2013b;Aakermann et al, 2015;Rouxel and Yokoyama, 2015). It is commonly believed that the surface strengthening against contact cracking comes from the linear superposition of a compressive stress (CS) profile onto the surface of the glass (Marshall and Lawn, 1978;Lawn and Fuller, 1984).…”